While the facts in this article are inherently flawed (the home version of MS Vista will indeed run on a Mac under Boot Camp), the premise behind this article brings up an interesting point that the Grid computing world has danced around for years, licensing issues.
In Grid computing, licensing concerns were more directed towards multiple instances of one application on several different machines, in the virtualization world the issue is "when is a machine not a machine".
The premise behind the above article (and I use the term premise loosely as I do not have a copy of the actual license myself, and I've seen the debate as to whether the Vista license is or isn't more restrictive in the context of a VM going on for several months now) is that MS Vista will require a more expensive version than the home version if one wants to run it on a VM. Whether true or not the debate itself sets an interesting precedence in that it has been rumored that one rather powerful software vendor has made the decision that "a virtual machine does not a machine make".
I guess it is all in the definition of "virtual"... and it will be interesting to see if any application vendors follow such a model.